Rain barrels are often used to collect rainwater for later use to irrigate landscapes or crops. They often will collect rainwater that has fallen on a roof or on a large hard ground surface, such as a paved parking lot or driveway. Many homeowners like the idea of conserving fresh water, and using rainwater for irrigation places less demand on wells or water supplies during drier periods.
Rain barrels may be integrated with sprinkler systems but during dry weather, a rain barrel may not have water to provide a sufficient amount for the plants being maintained. In that situation, a homeowner unsure of the quantity of water available may use a different source, such as a well or water supply, to ensure an adequate supply is available, leaving water in the rain barrel unused.